It comes as no surprise to learn, as you do in the preface to ''Too Brief a Treat,'' a new volume of Truman Capote's letters, that the author was as eccentric in his spelling as he was in pretty much everything else. Still, it's fascinating to find out that three words in particular gave him a lot of trouble -- so much so that Gerald Clarke, Capote's biographer and the editor of the letters, decided in the end to let them stand uncorrected in the published text. One of the three trips up a lot of people (''receive''). But the other two are generally less troublesome -- if only because one is a word that most of us dare not use of ourselves, and the other is a word we prefer not to use. Given all we know about Capote, his difficulties with both seem significant.

The first word was ''genius''- or, as Capote sometimes spelled it, ''genuis.'' At the beginning of his life and career the word cropped up often. ''We all thought he was a genius,'' said the writer Marguerite Young, after the diminutive, flamboyant youth arrived at Yaddo, the artists' colony, in the spring of 1946. Capote was then only 21, but had already attracted considerable attention. This was partly for his writing -- a couple of macabre short stories, published in Mademoiselle and Harper's Bazaar -- and perhaps more for his public antics. (He'd been fired from The New Yorker for impersonating an editor -- he was a copyboy -- and was a regular at El Morocco and the Stork Club, swank nightspots where he would appear with fashionable young women like Gloria Vanderbilt and Oona O'Neill.) At Yaddo, though, he worked hard: he was writing a novel for which he'd received a contract from Robert Linscott, an editor at Random House, who like so many others found Capote's combination of elfin charm and childlike vulnerability irresistible. ''Truman has all the stigmata of genius,'' Linscott declared in 1948, after publishing his first novel.

That novel was the career-making ''Other Voices, Other Rooms,'' an exercise in Southern Gothic that, as one newspaper put it, had ''critics in a dither, as they try to decide whether he's a genius.'' In fact, many if not most of the major critics dismissed the novel, an overspiced gumbo of rape, murder, homosexuality, disease, madness and transvestism. (''A minor imitation of a very talented minor writer, Carson McCullers,'' Elizabeth Hardwick wrote in Partisan Review.) What made the book was the sensational publicity over the author's jacket photo, which showed the 23-year-old Capote lying on a divan staring at the camera with the hungry look of a rent boy. Capote himself later acknowledged that it was the ''exotic photograph'' that marked ''the start of a certain notoriety that has kept close step with me these many years.''

When you pick up ''Other Voices'' today and slog through the Spanish-mossy plot and the overinflated sentences (''he knew now, and it was not a giggle or a sudden white-hot word; only two people with each other in withness''), it can be hard to see what the fuss was all about. And yet a powerful presence is unmistakable -- you can see how clearly the deliberate, almost Wildean aestheticism of Capote's prose stemmed from his outr?ose. Both excited an entire generation. Cynthia Ozick later recalled how brandishing a copy of ''Other Voices'' was like waving a banner against the ''blight'' of the drabness of the postwar milieu. Capote would work at the exquisiteness of his sentences until it became a hallmark of his mature style. Norman Mailer summed up the consensus of that generation of writers when he declared that Capote wrote ''the best sentences word for word, rhythm upon rhythm,'' of any of them.

Remarkably, Capote's child-prodigy persona carried him nearly into his 40's. ''Yes, he's a genius, Ma'am,'' Capote's friend Cecil Beaton told the queen mother late in 1962, when Capote was 38. But again it was unclear what, precisely, ''genius'' referred to. In the 15 years since ''Other Voices, Other Rooms'' he had added to his oeuvre just two slight novellas, ''The Grass Harp'' and ''Breakfast at Tiffany's,'' a few stories and a short book that grew out of a long New Yorker piece about touring the Soviet Union with the cast of ''Porgy and Bess'' (''The Muses Are Heard''). Still, the royal lady found him a genius -- quite wonderful, so intelligent, so wise, so funny'' over lunch, at which Capote laughed and whooped with joy ''when the summer pudding appeared,'' as Beaton later recalled. It is that last detail that suggests why it was so hard not to think of the author as remarkable: throughout his life he loved to play the child. People reacted accordingly. Again and again in the various biographies and memoirs of Capote, you're struck by how often and how naturally people would make the comparison. ''A precocious child, so cute and funny,'' Eleanor Lambert declared at the beginning of his career; a ''wonderful but bad little boy,'' David Selznick remarked, when Capote was 28.